Acquisition system for a long record length digital storage oscilloscope

ABSTRACT

A real time digital storage oscilloscope acquires a long data record in an acquisition memory and processes the data of the long data record to search for predetermined events. Upon detection of such a predetermined event, circuitry generates an event detect signal, and data comprising an acquisition frame surrounding the event is applied to a waveform processing and display system. The long data record can be replayed in order to perform additional searches throughout the data record using different search criteria, thereby permitting multiple waveforms to be displayed simultaneously, each being captured as a result of a different user-defined event. A screen display may be programmed to display a different kind of event such as Runt signal, Overshoot, or Pulsewidth Violation in each waveform, or to display multiple occurrences of the same kind of event such as Runt signal in each waveform.

FIELD OF THE INVENTION

[0001] The subject invention concerns, in general, the field of DigitalStorage Oscilloscopes (DSOs) having long record length capability, andconcerns in particular, an architecture for DSOs that provides improveddigital signal processing of long record length waveform data.

BACKGROUND OF THE INVENTION

[0002] The long-record-length features of modern long-record-lengthoscilloscopes are generally found to be very difficult and cumbersome tocontrol. That is, when one has collected 32 Mbytes of data in such adeep memory oscilloscope, how does one then use and interpret that data?For example, assume that the user wanted to scroll through the entirerecord looking for a particular event that caused a problem in thesystem under test. For such a visual scan, a scrolling-rate of about 500points per second is quite reasonable. That is, a particular point onwaveform would move across the screen from right to left in about 1.0second. Unfortunately, at this rate it would take approximately 17.5hours for the user to view the entire data record.

[0003] The fact that many oscilloscopes include a printer might lead oneto think that the solution to this problem would be to merely print outthe entire record. For such a print out, a resolution of 300 points perinch is quite reasonable. Unfortunately, if the user were to print outsuch a long record on paper at 300 points per inch (approximately 118points per cm), the printer would use 1.684 miles (2.6944 km) of paper.These two examples highlight the difficulty in dealing with largeamounts of data. It simply is not practical for the user to visuallyinspect all of the collected data for the anomalies that the user mustfind.

[0004] Modern DSOs attempt to solve this problem by waiting for atrigger event to occur, and then acquiring in memory a frame of waveformdata surrounding the event. The frame is then processed by waveform mathsoftware, measurement software, and display system software. All of thispost-processing creates extremely long periods of “dead time”, in whichthe DSO is incapable of acquiring and storing additional waveformsamples. As a result, the anomaly that the user is searching for mayoccur, and be missed.

[0005] More recent DSOs have attempted to reduce the “dead time” byphysically positioning Digital Signal Processing (DSP) ICs close to theacquisition memory to convert acquired waveform data to display datamore efficiently. This arrangement is sometimes referred to as a“FastAcq” mode of operation. Use of FastAcq circuitry has greatlyreduced the “dead time” between triggers, and increased the number ofsamples per second that are displayed. Unfortunately, the data framesprocessed by the FastAcq circuitry are not retained, and are thereforeunavailable for additional processing. Moreover, cycle-to-cyclemeasurements (for jitter measurement) are adversely affected by the useof FastAcq circuitry because the time relationship between successivetriggers is not maintained.

[0006] Another disadvantage of many current DSO architectures is a“bottleneck” that exists because they transfer all of the data fromacquisition memory to main memory for processing and display over arelatively slow (i.e., typically 30 Mb/sec.) data bus.

[0007] In order to address this transfer-rate issue, AgilentTechnologies, Inc. of Palo Alto, Calif., has recently introducedInfiniium MegaZoom deep-memory oscilloscopes employing a custom ASICthat optimizes the sample rate for a given sweep speed and sends onlythe waveform data needed for a particular front panel setting. MegaZoomprovides a waveform update rate that is approximately twenty-five timesgreater than conventional deep memory oscilloscopes.

[0008] Wavemaster™ oscilloscopes with X-Stream™ technology, manufacturedby LeCroy Corporation of Chestnut Ridge, N.Y. provide an alternativesolution to the transfer-rate problem. These oscilloscopes employ asilicon-germanium (SiGe) digitizer and a high-speed streaming bus totransfer data from an analog to digital converter (ADC) through anacquisition memory and into a memory cache for extraction of informationby software routines.

[0009] However, what is needed is an oscilloscope having the capabilityto repeatedly “loop through” the long data record in order to detectpredetermined anomalies and produce a lively and active display.

SUMMARY OF THE INVENTION

[0010] A real time digital storage oscilloscope acquires a long datarecord in an acquisition memory and processes the data of the long datarecord to search for predetermined events. Upon detection of such apredetermined event, circuitry generates an event detect signal, anddata comprising an acquisition frame surrounding the event is applied toa waveform processing and display system. The long data record can bereplayed in order to perform additional searches throughout the datarecord using different search criteria, thereby permitting multiplewaveforms to be displayed simultaneously, each being captured as aresult of a different user-defined event. A screen display may beprogrammed to display a different kind of event such as Runt signal,Overshoot, or Pulsewidth Violation in each waveform, or to displaymultiple occurrences of the same kind of event such as Runt signal ineach waveform.

BRIEF DESCRIPTION OF THE DRAWING

[0011]FIG. 1 is a simplified block diagram of the architecture for aconventional deep-memory digital storage oscilloscope, as known from theprior art.

[0012]FIG. 2 is simplified block diagram of the architecture of aMegaZoom deep-memory digital storage oscilloscope, as known from theprior art.

[0013]FIG. 3 shows a simplified block diagram of an acquisitionarchitecture employing an FPGA for use in a digital storageoscilloscope, as known from the prior art.

[0014]FIG. 4 shows a more detailed block diagram of the acquisitionarchitecture of FIG. 1, as known from the prior art.

[0015]FIG. 5 shows a block diagram of an acquisition architectureemploying a first arrangement of a processor and an acquisition memoryfor use in a digital storage oscilloscope in accordance with the subjectinvention.

[0016]FIG. 6 shows a block diagram of an acquisition architectureemploying a second arrangement of a System Processor and an acquisitionmemory for use in a digital storage oscilloscope in accordance with asecond embodiment of the subject invention.

[0017]FIG. 7 shows a front panel arrangement of digital storageoscilloscope suitable for use with the invention.

[0018]FIG. 8 is a simplified flowchart showing a Primary Acquisition andPost Acquisition Trigger Event Search routine, in accordance with thesubject invention.

[0019]FIG. 9 is an illustration of a screen display in accordance with afirst aspect of the subject invention.

[0020]FIG. 10 is an illustration of a screen display in accordance witha second aspect of the subject invention.

DETAILED DESCRIPTION OF THE DRAWING

[0021]FIG. 1 shows a highly simplified block diagram of a conventionalfour-channel deep-memory digital storage oscilloscope, as known from theprior art. Each channel has a respective analog-to-digital (A/D)converter 131, 132, 133, 134 for receiving an analog signal from acircuit under test via a probe and cable arrangement (not shown). A/Dconverters 131, 132, 133, 134, apply digital samples of their respectiveanalog signal to a Deep-Acquisition Memory arrangement 150. The term“Deep-Acquisition Memory” means a memory capable of storing data recordsof millions of points to billions of points in length. A CPU 170 thenprocesses all of the data of the data record for ultimate display on adisplay screen 180. There are two distinct problems associated with thistype of architecture. First, CPU 170 forms a “bottleneck” in that ittakes a significant amount of time to transfer such huge data records,resulting in dead time before another acquisition can be made. Second,CPU 170 may use an inordinate amount of computing resources to compress,for example, 32 Mpoints down to 500 points for display. Unfortunately,this expenditure of computing resources most often results in a viewablewaveform that is of very little use to the operator.

[0022] In FIGS. 1 through 5, similarly numbered elements have similarfunctions which need not be described again. FIG. 2 shows a simplifiedblock diagram of the aforementioned Agilent Technologies Infiniiumoscilloscope with the MegaZoom feature. The MegaZoom feature employs acustom Application Specific Integrated Circuit (ASIC) 235 interposedbetween the A/D converters 231, 232, 233, 234 and The Deep AcquisitionMemory unit 250. ASIC 235 communicates with a front panel (not shown)and optimizes the sample rate for a given sweep speed and sends to theCPU 270 only that waveform data needed for a particular front panelcontrol setting. This operation significantly reduces the bottleneckdescribed above, and provides for the display of a more meaningfulsignal.

[0023]FIG. 3 shows a highly simplified block diagram of an architecturethat may be similar to that used in the above-mentioned LeCroyWaveMaster™ with X-Stream™ capability. This architecture is asignificant improvement over that of FIG. 1 in terms of its ability totransfer data quickly from the acquisition system to the processing anddisplay system. These oscilloscopes employ a silicon-germanium (SiGe)digitizer 355 which may be an FPGA and a high-speed streaming bus 390 totransfer data from an analog to digital converter (ADC) 331, 332, 333,334 through a Deep Acquisition Memory 350 and into a Memory Cache 370for extraction of information by software routines.

[0024]FIG. 4 is a more detailed view of the architecture of theacquisition system of a conventional deep memory oscilloscope. Referringto FIG. 4, Buffer amplifiers 401, 402, 403, 404, are associated withrespective oscilloscope channels. Each of Buffer amplifiers 410, 402,403, and 403 amplifies analog signal applied to its input and appliesthe buffered signal to a Track & Hold unit 410 and to a Trigger ASIC420. Track & Hold unit 410 is basically an analog switch used to routesignals to the A/D Converters according to different interleaveconfigurations. Track & Hold unit 410 also stabilizes the input signaland presents it to an A/D Converter 431, 432, 433, 434.

[0025] A Demultiplexer unit (DEMUX) 441, 442, 443, 444 is itself an ASICthat receives the digitized samples of the input signal from the A/DConverters 431, 432, 433, 434 and also receives trigger signals fromTrigger ASIC 420. As is well known, an A/D Converter produces datasamples at a rate that is faster than a memory can store them. To solvethis problem, a demux is used to reduce the rate at which memory-writeoperations occur by temporarily accumulating a series of high-speed datasamples from the A/D and then storing in memory perhaps 16 to 32 ofthese samples in a single memory-write operation. In this way, thememory is allowed sufficient time to store its data before beingpresented with the next group of newly acquired data samples. In theabsence of a trigger signal, the demux ASICs continuously write datainto memory. When a trigger signal is received, the demux ASICs continueto write data into memory for only as long as necessary to store therequired amount of post trigger data. At that time, data storage isstopped until a signal is received indicating that the acquisitionmemory has been unloaded into the processing system of the oscilloscope.Thus, DEMUX 441, 442, 443, 444 controls the flow of data into DeepAcquisition Memory 451, 452, 453, 454.

[0026] Unfortunately, none of the architectures illustrated in FIGS. 1through 4 allows a user to repeatedly “loop through” the long datarecord, while triggering on different criteria, and observe the resultin a lively and active display. An operator may realize that an anomalyis present in the signal under test and that the anomaly is causing aproblem. However, he may not know what the anomaly is. How does one setup a trigger if one does not know if the anomaly is taking the form ofrunt, or pulse width problem, or even a missing pulse? Thus, it isimportant to be able to trigger on different criteria to detect the“unexpected” form of the variant, by changing the triggering criteria asone continuously loops through the long data record.

[0027] Such an oscilloscope architecture is shown in FIG. 5, and thesubject invention will now be described with respect to FIGS. 5, 6, 7,and 8. Since FIGS. 4 and 5 are identical with the exception of the closephysical and logical association of a Processor unit (PROC.) 561, 562,563, 564, with a Deep Acquisition Memory 551, 552, 553, 554, previouslydescribed elements need not be described again.

[0028] In the apparatus of FIG. 5, a single channel (e.g., CH 1) is usedto supply all of the signal to be examined. In this regard, all ofacquisition memories 551, 552, 553, and 554 are concatenated to form asingle long record length memory for the signal received from viaoscilloscope channel 1. Processor unit (PROC.) 561, 562, 563, 564, maybe a microcomputer, but preferably is an FPGA (Field Programmable GateArray) because an FPGA is capable of processing data up to 100× fasterthan a microcomputer (i.e., up to 100× faster than an Intel Pentium IV®microcomputer). Deep Acquisition Memory 551, 552, 553, 554 has a datapath DATA1, DATA2, DATA3, DATA4, coupled to a bus leading to a SystemProcessor 570, that is, to its normal waveform data processing path.Note that Processor unit 561, 562, 563, 564 also has a data output pathlabelled, TIME STAMP, also coupled to the bus for providing time stampsdefining the frames of data to be processed and displayed. Processorunit 561, 562, 563, 564 also provides at least one trigger-type signalEVENT DET. (Event Detect). It is envisioned that EVENT DET. may in factbe multiple event detection signal lines coupled to System Processor570. Each trigger output is latched so that it can later be read todetermine which trigger event caused the post acquisition data frame tobe processed. Processor unit 561, 562, 563, 564 may be a singleprocessor controlling all acquisition memories, or a plurality ofprocessors wherein each processor is associated with a portion of theacquisition memory (as shown in FIG. 5). With the illustratedarrangement of processing units in all channels, both parallelsimultaneous triggering on predefined events is easily accomplished.Communication lines between the Processor unit 561, 562, 563, 564 arenot shown for simplicity.

[0029]FIG. 6 shows an embodiment of the invention in which the systemprocessor is programmed to also perform the function of post acquisitionexamination of the acquisition memory for the occurrence of specificpredetermined events. In the embodiment of FIG. 6, no separate processorunit is employed. Since FIGS. 5 and 6 are identical with the exceptionof the close logical association of a System Processor 670 with a DeepAcquisition Memory 651, 652, 653, 654, previously described elementsneed not be described again.

[0030] System Processor 670 may be a microcomputer such as, an IntelPentium IV® microcomputer. Deep Acquisition Memory 651, 652, 653, 654has a data path DATA1, DATA2, DATA3, DATA4, coupled to a bus leading toSystem Processor 670, that is, to its normal waveform data processingpath. Because System Processor 670 is performing the event searchitself, there is no need for generating an EVENT DET. (Event Detect)signal, as was done in the embodiment of FIG. 5. With the illustratedarrangement of FIG. 6, System Processor 671 examines post-acquisitiondata acquired in all channels and permits simultaneous display of alldetected predefined events on a display screen of the oscilloscope.

[0031]FIG. 7 shows a front panel 700 for an oscilloscope having controlssuitable for use with the subject invention. The oscilloscope controlsare arranged in functional groups 710, 720, 730, 740, and 750.Functional groups 740 and 750 are arranged together in a furtherfunctional group 760. Front panel 700 includes standard control buttonssuch as CURSORS and AUTOSET and other control knobs that will not bedescribed in detail. Functional group 710 includes controls for menuselection, for selecting a channel, and for adjusting the scale andposition of the displayed signal waveform. Functional group 720 controlsthe timebase aspects of the signal to be acquired, such as Delay,Resolution, Record Length, and Sample Rate. Functional group 730controls the Display and includes controls for Horizontal Position,Vertical Position, Vertical Scale and Horizontal Scale.

[0032] Functional group 770 includes Functional groups 740 and 750, andalso a set of controls for controlling how the oscilloscope is toacquire the waveform samples of the signal under test. Specifically, abutton is provided for displaying an Acquire menu on the display screenof the oscilloscope. A second button, labelled MODE, selects amongREGULAR MODE, DUAL MODE, AND FastAcq MODE. An indicator located next toeach of these legends illuminated to show which mode is selected. Theilluminated indicator is depicted in FIG. 7 by a crosshatched pattern.When an operator wants to acquire a long length data record for PostAcquisition Search for Secondary Trigger Events, he selects DUAL MODE.In this mode the primary data acquisition record length is set tomaximum, and the Post Acquisition Record length (Frame size) is set bythe Record Length control of Functional group 720. Functional Group 740controls the Post Acquisition Event Search and includes a MENU buttonfor displaying a menu including a list of trigger event criteria. Notethat “replay” of the long length data record is controlled by pushbuttoncontrols that are similar in form and function to the controls of a VCR.In functional group 740, indicators are illuminated to show that a PostAcquisition Event Search is active, and that the long record length datais being played in a forward direction. Functional group 740 alsoincludes a SCROLL knob for manually scrolling through a paused longrecord length waveform from one event to the next. Functional group 750contains standard triggering controls and indicators.

[0033]FIG. 8 is a simplified flowchart showing a Primary Acquisition andPost Acquisition Trigger Event Search routine. The routine is entered atlocation 800 and advances to block 810 wherein the oscilloscope acquiresa long record primary acquisition using standard criteria for primarytriggering. After acquiring the long record, the routine advances tostep 820 wherein Processor unit 561, 562, 563, 564 (preferably a highspeed FPGA) of FIG. 5 (or System Processor 671) searches the stored longrecord data in a Post Acquisition Event Search for a secondary triggerevent. At step 830, a check is made to see if the event of interest wasfound. If not, the routine continues looking for it within the acquiredlong record data. If so, then the routine advances to step 840 wherein aframe of data surrounding the event is sent to the waveform processingsection of the oscilloscope, and a secondary trigger is generated. Atstep 850, the frame of Post Processing Trigger data is processed and theresulting waveform is displayed. A determination is made at step 860 ofwhether or not the end of the long record data has been reached. If not,the routine loops back to step 820 and continues looking for the triggerevent within the long record data. If so, the routine advances to step860 to see if the oscilloscope is in One-Shot acquisition mode, or inFree-Run mode. If in One-Shot acquisition mode, no new data should beacquired, so the YES path is followed to step 820 and the search beginsagain within the previously acquired long record data. If in Free-Runmode (sometimes called Autorun mode), a new long record lengthacquisition will be performed, so the routine loops back to step 810 toacquire the new record before looking through it for Post AcquisitionEvents (anomalies).

[0034] There is a purpose for looping back to step 820 to continuesearching through the previously acquired long record data when the PostAcquisition Search Event was not found. By doing so, the routine createsa lively responsive display because the user can change the searchcriteria and immediately see a change on the display. For instance, theoperator may have set the Post Acquisition Search Event to be a Runtsignal event (i.e., a detection of a pulse whose amplitude did not reacha switching threshold before returning to its original state). Duringthe search the operator may change his mind and wish to search for apulse having an out-of-tolerance pulse width. Immediately upon adjustingthe search criteria, the displayed waveform will reflect the result ofthe new choice of event. That is, event types may be changed on-the-flyas the long record length acquisition is being scanned.

[0035]FIG. 9 is an illustration of a screen display produced inaccordance with the subject invention. A display screen 900 of a digitalstorage oscilloscope is shown displaying four waveforms 901, 902, 903,904. Each waveform is exhibiting an anomaly that was detected andtime-stamped by apparatus according to the subject invention. Associatedwith each waveform is a Record Bar 911 and pointers 921 a, 921 b, 921 c,921 d, 922 a, 922 b, 923 a, 924 a. The Record Bar is provides anindication of the relative length of the record, and the positions ofthe pointers within the Record Bar are representative of the approximatelocations of the anomalies (i.e., Events) within the long data record.

[0036] As noted above, the long data record is acquired by using thecriteria set in accordance with the normal trigger menu. The long datarecord is stored by concatenating all of the acquisition memory from allfour data channels. A single channel is then assigned to be the conduitfor the signal under test. Referring again to FIG. 9, an EVENT SOURCEmenu 930 allows selection of the source waveform that will be searchedfor anomalies. The menu choices are selected in sequence by repeatedpressing of a pushbutton 935. In this case, the Acq Wfm choice ishighlighted to indicate that an acquired waveform has been selected tobe the source waveform. Other choices are either of a Math Waveform(MathWfin), or a reference waveform (Ref Wfm). Because AcqWfm wasselected, the next choice is that of the data channel, in this case,Chan 1 has been highlighted to indicate its selection. As is well-knownin the oscilloscope art, as each channel is deselected, its associatedmemory is applied to the remaining channels, thereby increasing theirmemory depth. The long record length referred to in this application isthe entire acquisition memory associated with a single channel. Any ofthe four channels may be selected (one at a time) as the source channel.After the long data record is acquired, the data is searched foranomalies in a post-processing operation involving detection of thevarious anomalies and time-stamping their respective locations inmemory.

[0037] While in this example four waveforms are displayed, one skilledin the art will recognize that the invention is extendible to more thanfour. Each of the four waveforms W1, W2, W3, W4 is controlled to displayan anomaly (i.e., Event) chosen from a respective event menu 951, 952,953, 954, by repeatedly pressing an associated pushbutton 961, 962, 963,964. In this case, W1 displays examples of Runt signals, W2 displaysexamples of Pulsewidth violations, W3 displays examples of Undershootconditions, and W4 displays examples of Fall time violations. Processor561, 562, 563, 564, or System Processor 670, extracted short recordlength waveforms 901, 902, 903, 904 from the long record length datastored in acquisition memory, in response to a search for preselectedanomalies (i.e., Post acquisition Search Events).

[0038] The legend displayed to the left of the waveform 901 indicatesthe source C1 (channel 1), the selected kind of anomaly W1, and theoccurrence number of that kind of event in the long data record E1. Thatis waveform 901 is displaying the first occurrence 921 a of a runttrigger in the long data record. Similarly, waveforms 902, 903, 904 aredisplaying the first occurrence of their respective kind of anomaly 922a, 923 a, 924 a in the long data record, where pointer 921 b indicatesthe second occurrence of a Runt signal in the long data record, and soon.

[0039] Selecting a waveform (for example, by physically touching thewaveform on a touch-sensitive screen) logically connects the SCROLL knob975 to that waveform. Thereafter, rotating the SCROLL knob 975 causesthe waveform to jump to a display of the next example of that kind ofevent, wherever it occurs in the long data record. For example, rotatingSCROLL knob 975 will cause the runt signal associated with pointer 921 bto be displayed and to be labelled C1W1E2 (the second event of thatkind). Selecting the second event will also cause pointer 921 b to behighlighted, and pointer 921 a to no longer be highlighted. SCROLL knob975 is the same control labelled SCROLL in functional group 740 of FIG.7.

[0040] Each of the waveforms is displayed with its anomaly centeredon-screen (as shown by dotted vertical line 915) for ease of use. Asnoted above each event is surrounded by data, the number of samples ofwhich is determined by rotation of an EVENT RECORD LENGTH knob 985.Numeric display 980 indicates that 1.6 μs of time surrounds the event ofinterest, and each of waveforms 901, 902, 903, 904 includes the samenumber of samples surrounding the event of interest. Note that there isno time relationship between the displayed waveforms.

[0041] Because waveform 901 is associated with pointers 921 a, 921 b,921 c, 921 d, it is envisioned that they be displayed in the same uniquecolor (e.g., red). Similarly, waveform 902 is associated with pointers922 a, 922 b and both should be displayed in a second unique color(e.g., yellow). Waveform 903 is associated with pointer 923 a and bothshould be displayed in a third unique color (e.g., green). Waveform 904is associated with pointer 924 a and both should be displayed in afourth unique color (e.g., blue). As noted above, the particular pointerassociated with the anomaly currently displayed on-screen will behighlighted to indicate its position in the long data record (see 921 a,922 a, 923 a, 924 a).

[0042] While the operation of apparatus of the invention with respect toFIG. 9 is quite useful, one may wish to view all occurrences of singleanomaly within the long data record. The screen display of FIG. 10provides an easy way to accomplish this goal. The majority of theelements of FIG. 10 is identical to similarly numbered elements of FIG.9, and need not be described again. Event selection menus 1051, 1052,1053, 1054 are used to program all of waveforms W1, W2, W3, W4 todisplay the same kind of event, a Runt signal. All pointers in RecordBar 1011 have been removed except for those 1021 a, 1021 b, 1021 c, 1021d, 1021 e that indicate the relative positions of runt signals in thelong data record. Note that waveform W2 is labelled C1W2E2 to indicatethat it is displaying the second runt trigger found, waveform W3 islabelled C1W3E3 to indicate that it is displaying the third runt triggerfound, but waveform W4 is labelled C1W4E5 to indicate that it has beenadjusted with SCROLL KNOB 1075 to display the fifth runt trigger found.In this regard, note that pointers 1021 a, 1021 b, 1021 c, and 1021 eare highlighted, but 1021 d is not highlighted.

[0043] Some examples of Post Acquisition Search Events (anomalies) are:Jitter (width, rise, edge, etc.) Edge High Pulse width Low Pulseamplitude Min Rise time Max Fall time Max Telecom serial pattern RMSTelecom packet recognition Overshoot + − Wave Shape (matched filter)Histogram, stdev, mean, pk-pk Runt Eye Diagrams and mask triggersWaveform Comparisons Limits masks Peak-to-peak Frequency Period

[0044] One skilled in the art will appreciate that this list does notinclude all possible trigger events, and the scope of the followingclaims is intended to be broad enough to include those trigger eventsnot specifically recited.

[0045] The term DUAL MODE has been used in describing the mode ofoperation of the subject invention. Use of this term is not critical tothe practicing of the subject invention, nor is this term is to beconsidered limiting in any way.

[0046] What has been described is a novel acquisition system for a longrecord length DSO that solves the “bottleneck” problem by onlytransferring the data of interest to the main processing section of theoscilloscope. Also, the subject acquisition system maintains the data ofthe entire long record in memory, thus preserving the timestamps of thedata to allow post processing jitter analysis to be performed.

[0047] Throughout the specification the terms “event” and “anomaly” havebeen used interchangeably to indicate a point of interest in the longdata record.

[0048] While four Processing units 561, 562, 563, 564 have been shown,and described above, other arrangements employing only a singleprocessing unit may be used, and are considered to be within the scopeof the invention and covered by the following claims. The use ofProcessing unit in each channel permits simultaneous triggering ondifferent criteria in each channel, thus permitting simultaneous displayof waveforms relating to each trigger.

[0049] One skilled in the art will recognize that a given processingunit may be programmed to recognize more than one kind of anomalousevent.

[0050] While the four Processing units 561, 562, 563, 564 have beendescribed as preferably being FPGAs, one skilled in the art willunderstand that use of a microcomputer in this role will also work in anacceptable manner, but the speed advantage of the FPGA will not berealized. Therefore the use of a microcomputer, ASIC, or other processorunit is considered to be within the scope of the invention and coveredby the following claims.

What is claimed is:
 1. Acquisition System for a long record lengthdigital oscilloscope, comprising: an input terminal for receiving asignal under test; an analog-to-digital converter having an inputcoupled to said input terminal for receiving said signal under test, andproducing digital samples of said signal under test at an output; atrigger circuit having an input coupled to said input terminal forreceiving said signal under test, and producing a trigger signal at anoutput in response to detection of a predetermined trigger event in saidsignal under test; an acquisition memory for storing said digitalsamples of said signal under test in a data record; and processorcircuitry for examining said stored digital samples in a postacquisition mode of operation and producing an event detect signal inresponse to detection of a predetermined event in said stored digitalsamples, and causing a predetermined amount of said stored digitalsamples to be read from said acquisition memory and sent to a signalprocessing portion of said oscilloscope for processing and display; saidpredetermined amount of said stored digital samples being less than thewhole data record and being related in time to said event detect signal.2. The acquisition system of claim 1 wherein: said processor operates inone of a one-shot mode and an Autorun mode; in said one-shot mode, saidprocessor repeatedly examines a single data record; in said Autorunmode, said processor causes the acquisition of a new data record uponcompletion of examination of a currently stored data record.
 3. Theacquisition system of claim 2 wherein: data representative of saidpredetermined event is input to said processor by a user for causingsaid processor to produce said event detect signal upon detection ofsaid event.
 4. The acquisition system of claim 3 wherein: said processoris responsive to input data entered by a user for changing said datarepresentative of said predetermined event; said input data entered bysaid user is accepted by said processor before or during saidexamination of said data record.
 5. The acquisition system of claim 4wherein: said predetermined amount of stored digital samples representsa frame of samples surrounding said second trigger event, and amagnitude of said predetermined amount of stored digital signals iscontrollable by said user.
 6. The acquisition system of claim 5 whereinsaid oscilloscope has multiple channels: each of said channels having along record length memory associated therewith; each of said long recordlength memories being concatenated with the others to form a single longrecord length memory.
 7. The acquisition system of claim 6 wherein saidoscilloscope has multiple channels: each of said channels having a longrecord length memory associated therewith; and said processor comprisesindividual processing units each of which is associated with arespective one of said long record length memories of said channels. 8.The acquisition system of claim 7 wherein: each of said individualprocessing units can be programmed to detect a plurality of differentevents; and waveforms representative of data surrounding each of saidrespective different events are simultaneously displayed on a displayscreen of said oscilloscope.
 9. The acquisition system of claim 6wherein said processor is an FPGA.
 10. The acquisition system of claim 6wherein said processor is a microcomputer.
 11. The acquisition system ofclaim 6 wherein said processor is an ASIC.
 12. The acquisition system ofclaim 7 wherein said processor is an FPGA.
 13. The acquisition system ofclaim 7 wherein said processor is a microcomputer.
 14. The acquisitionsystem of claim 7 wherein said processor is an ASIC.
 15. A long recordlength digital oscilloscope, comprising: an input terminal for receivinga signal under test; an analog-to-digital converter having an inputcoupled to said input terminal for receiving said signal under test, andproducing digital samples of said signal under test at an output; atrigger circuit having an input coupled to said input terminal forreceiving said signal under test, and producing a trigger signal at anoutput in response to detection of a predetermined trigger event in saidsignal under test; an acquisition memory for storing said digitalsamples of said signal under test in a data record; a demultiplexer unitcoupled between said analog-to-digital converter and said acquisitionmemory for receiving said digital samples and controlling the flow ofsaid samples to said acquisition memory in response to said triggersignal received from said trigger circuit; processor circuitry forexamining said stored digital samples in a post acquisition mode ofoperation and producing an event detect signal in response to detectionof a predetermined event in said stored digital samples, and producingmemory address signals indicative of a range of memory locationscontaining data relating to said predetermined event; and a systemprocessor for causing a predetermined amount of said stored digitalsamples to be read from said acquisition memory and sent to a signalprocessing portion of said oscilloscope for processing and display inresponse to said event detect signal and said memory address signals;said predetermined amount of said stored digital samples being less thanthe whole data record and being related in time to said event detectsignal.
 16. The long record length digital oscilloscope of claim 15wherein: said processor operates in one of a one-shot mode and anAutorun mode; in said one-shot mode, said processor repeatedly examinesa single data record; in said Autorun mode, said processor causes theacquisition of a new data record upon completion of examination of acurrently stored data record.
 17. The long record length digitaloscilloscope of claim 16 wherein: data representative of saidpredetermined event is input to said processor by a user for causingsaid processor to produce said event detect signal upon detection ofsaid event.
 18. The long record length digital oscilloscope of claim 17wherein: said processor is responsive to input by a user for changingsaid data representative of said predetermined event; said input by saiduser is accepted by said processor before or during said examination ofsaid data record.
 19. The long record length digital oscilloscope ofclaim 18 wherein: said predetermined amount of stored digital samplesrepresents a frame of samples surrounding said second trigger event, anda magnitude of said predetermined amount of stored digital signals iscontrollable by said user.
 20. The long record length digitaloscilloscope of claim 19 wherein: said processor can be programmed todetect a plurality of different events; and waveforms representative ofdata surrounding each of said respective different events aresimultaneously displayed on a display screen of said oscilloscope. 21.The long record length digital oscilloscope of claim 20 wherein saidprocessor is an FPGA.
 22. The long record length digital oscilloscope ofclaim 21 wherein said processor is a microcomputer.
 23. The long recordlength digital oscilloscope of claim 22 wherein said processor is anASIC.
 24. A long record length digital oscilloscope, comprising: aninput terminal for receiving a signal under test; an analog-to-digitalconverter having an input coupled to said input terminal for receivingsaid signal under test, and producing digital samples of said signalunder test at an output; a trigger circuit having an input coupled tosaid input terminal for receiving said signal under test, and producinga trigger signal at an output in response to detection of apredetermined trigger event in said signal under test; an acquisitionmemory for storing said digital samples of said signal under test in adata record; a demultiplexer unit coupled between said analog-to-digitalconverter and said acquisition memory for receiving said digital samplesand controlling the flow of said samples to said acquisition memory inresponse to said trigger signal received from said trigger circuit; anda system processor for examining said stored digital samples in a postacquisition mode of operation for detecting a predetermined event insaid stored digital samples; said system processor causing apredetermined amount of said stored digital samples to be read from saidacquisition memory and sent to a signal processing portion of saidoscilloscope for processing and display in response to said detection ofsaid predetermined event; said predetermined amount of said storeddigital samples being less than the whole data record and being relatedin time to said event detect signal.
 25. The long record length digitaloscilloscope of claim 24 wherein said oscilloscope has multiplechannels: each of said channels having a long record length memoryassociated therewith; each of said long record length memories beingconcatenated with the others to form a single long record length memory;said system processor being capable of being programmed to detect aplurality of predetermined events in data stored in said single longrecord length memory; and waveforms representative of data surroundingeach of said respective predetermined events are simultaneouslydisplayed on a display screen of said oscilloscope.
 26. The long recordlength digital oscilloscope of claim 25 wherein said system processor isan FPGA.
 27. The long record length digital oscilloscope of claim 25wherein said system processor is a microcomputer.
 28. The long recordlength digital oscilloscope of claim 25 wherein said system processor isan ASIC.
 29. A method for use in an oscilloscope for displaying awaveform of interest extracted from an acquisition of a long datarecord, comprising the steps of: acquiring a long data record in anacquisition memory; examining the data of the long data record in a postprocessing mode of operation for the occurrence of a user-defined event;upon detection of such a predetermined event, applying data comprisingan acquisition frame surrounding the event to a waveform processing anddisplay system.
 30. The method of claim 29 wherein: said long datarecord is replayed to perform said examining and said applying stepsthroughout the data record using different predetermined searchcriteria; and wherein said applying step causes multiple ones of saidwaveforms of interest to be displayed simultaneously, each beingcaptured as a result of a different user-defined event.
 31. The methodof claim 29 wherein said long data record is replayed to perform saidexamining and said applying steps throughout the data record using asingle search criterion; and wherein said applying step causes multipleones of said waveforms of interest to be displayed simultaneously, eachbeing captured as a result of a single user-defined event.